| In the context of global climate changes,the increase of carbon dioxide(CO2)concentration,temperature and shift in precipitation will directly affect soil nutritional status,thereby affecting vegetation growth and soil microbial community diversity.The ecological environment in arid and semi-arid areas is fragile and extremely sensitive to climate change.As the core component of arid and semi-arid ecosystems,how these plants respond to and adapt to climate change is an important problem to be solved,which will directly affect the stability of ecosystem structure and function.Rhizosphere soil is an area of plant-microorganism interaction.And rhizosphere soil microorganisms have important effects on plant growth and ecological adaptability.Studying the response of rhizosphere soil microbial diversity and community structure to environmental change and its driving factors in arid and semi-arid areas is of great significance for understanding the ecological adaptation mechanism of constructive plants under future climate change.Therefore,this study took Caragana liouana and C.microphylla as the research objects,analyzed the diversity and community structure characteristics of bacteria,fungi and archaea in rhizosphere soil of two different geographic populations of Caragana,clarified the main driving factors affecting soil microbial diversity and community structure,explored the relative roles of the deterministic and stochastic processes in the assembly of soil microbial community,revealed the response and adaptation mechanism of Caragana to drought environment,and also provided basic data for the research,protection and development of soil microbial diversity of desert plants.The main finding are as follows:(1)22 phyla,62 classes,131 orders,185 families,and 304 genera were identified from all rhizosphere soil of C.liouana and C.microphylla.At the phylum level,Proteobacteria,Acidobacteria,Bacteroidetes and Actinobacteria were the most abundant phyla.And the abundance of Alphaproteobacteria,Gemmaproteobacteria and Bacteroidia were higher at the class levels.At genus level,Rhizobium,Sphingomonas,RB41 and Bacillus were dominant.The principal coordinate analysis and ANOSIM demonstrated that there were significant differences between them in the bacterial community structure.Based on the redundancy analysis,altitude were the main ecological factors associated with soil bacterial diversity,and pH,electrical conductivity,altitude and aridity index were the dominant factors associated with changes in the rhizosphere bacterial community structure.With the increase of geographical distance,the β-diversity of soil bacteria community decreased significantly.Variance partitioning analysis(VPA)and Mantel analysis showed that both environmental factors(pH,EC,ALT and AI)and spatial variables played roles in the assembly of soil bacterial community.(2)7 phyla,20 classes,43 orders,66 families,and 78 genera were identified from all rhizosphere soil of C.liouana and C.microphylla.At the phylum level,Ascomycota,Basidiomycota and Zygomycota were the most abundant phyla.And the abundance of Eurotiomycetes,Sordariomycetes,Agaricomycetes and Dothideomycetes were higher at the class levels.At genus level,Penicillium,Unclassified_f_Unidentified,Geomyces and Mortierella were dominant,and we also found Rhizophagus and Glomus in rhizosphere soil.Soil fungi Chao1 index,ACE index and Simpson index were lower in the rhizosphere of C.liouana.The principal coordinate analysis and ANOSIM demonstrated that there were significant differences between them in the fungal community structure.Based on the redundancy analysis,soil organic carbon,total nitrogen,electrical conductivity,available potassium,altitude,total phosphorus and aridity index were the main ecological factors associated with soil fungal diversity,and altitude,available potassium and total phosphorus were the dominant factors associated with changes in the rhizosphere fungal community structure.With the increase of geographical distance,the β-diversity of soil fungi community decreased significantly.Variance partitioning analysis(VPA)and Mantel analysis showed that both environmental factors(ALT,AK and TP)and spatial variables played roles in the assembly of soil fungal community.(3)4 phyla,5 classes,5 orders,6 families,and 7 genera were identified from all rhizosphere soil of C.liouana and C.microphylla.At the phylum level,Thaumarchaeota,Unclassified,Euryarchaeota and Nanoarchaeota were the most abundant phyla.And the abundance of Nitrososphaeria,Unclassified,Thermoplasmata,Woesearchaeia,Halobacteria and Nanohaloarchaeia were higher at the class levels.At genus level,Unclassified_f_Nitrososphaeraceae,Unclassified,Candidatus Nitrocosmicus and Candidatus Nitrososphaera were dominant.The archaeal Shannon index and Simpson index of C.microphylla were significantly higher than those of C.liouana.The principal coordinate analysis and ANOSIM demonstrated that there were significant differences between them in the archaeal community structure.Redundancy analysis showed that soil organic carbon were the dominant factors associated with changes in the rhizosphere archaeal community structure.With the increase of geographical distance,the β-diversity of soil archaea community decreased significantly.Variance partitioning analysis(VPA)and Mantel analysis showed that both environmental factors(SOC)and spatial variables played roles in the assembly of soil archaeal community.In conclusion,environmental factors predominantly determined the structural of bacterial,fungal and archaeal community structure in the rhizosphere soil of Caragana species in semi-arid regions.And there was a significant negative relationship between geographical distance and microbial community structure.The result indicated that the deterministic versus stochastic processes jointly drive the assembly microbial communities of Caragana species. |
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